The following invention relates to a training device for athletes and more particularly, to a video system which may be used by student athletes engaged in a sports activity in order to match their dynamic technique with that of a recognized master in the field.
There are a number of visual systems that provide overlays by superimposing two dynamic video representations of the same activity. Such systems are shown, for example, in Michaels et al. U.S. Pat. No. 4,015,344, Haas et al. U.S. Pat. No. 4,137,566, McCullough et al. U.S. Pat. No. 3,408,750 and Seidel et al. U.S. Pat. No. 4,828,500.
All of these references make use of a directly recorded image of the master, such as on video tape, taken while the master is performing a particular dynamic technique and provide the student with a means of overlaying an image of his own technique against that of the master in order to determine what deviations exist. These systems, however, are difficult to use and to calibrate. Because of the different sizes and positions of the images, it is hard to exactly overlay the two images. Further, the two images are time based. That is, because they are dynamic representations of the sports activity, in order to be useful to the student the movements must take place at the same relative time. This is especially true in a context in which the positions of the body and its extremities, or equipment such as a bat, tennis racket, or golf club, are to be compared at different points of the stroke.
In many athletic endeavors, however, the rate of speed at which an activity is performed is not as important as the position of the hands, arms, or feet at different times during the movement. For example, a golf swing is highly dependent upon maintaining certain desired positions of the hands, the arms, the head, and the position of the club at various points during the swing. Moreover, these time-based systems, are difficult for a student to use interactively, that is, as he or she is actually performing the technique. During practice of a golf swing, for example, as the student is observing the moving image of the master on the overlaid display, the student would not only have to match the various arm, head, and club head positions of the master, but would also have to swing the club with the same degree of force (which is time dependent) in order to affect a valid comparison at all points during the swing.
An alternative type of system is shown in Mann, U.S. Pat. No. 4,891,748. In this system, a computer-generated image is made representing the cumulative technique of several masters. This image is scaled, by the computer, to the size of the student's image and is advanced, frame-by-frame, on the overlay display, so that the student can imitate the static pose recorded in each frame. Unless there is someone available who is willing to assist with this system, however, the student must either select each frame, forcing the student to repeatedly break his own stance while selecting the individual frames representing a particular movement, or rely on automatic frame advancement, forcing the student to keep pace with the preselected rate at which the frames are advanced. Moreover, the elaborate software needed to operate this system is expensive to develop and must be customized for each individual student.
Less complex systems are known that use a mirror to perform an overlay function, such as those shown in Light U.S. Pat. No. 3,611,591 and Casey U.S. Pat. No. 3,915,457. In Casey, for example, a transparent sheet bearing an image of the master in a number of different poses is set directly over a convex mirror, thereby forming an overlay together with the image of the student reflected in the mirror. Only a relatively limited number of poses can be represented with clarity on any one sheet, however, forcing the student to repeatedly interrupt practice to replace transparencies. Moreover, with such systems, the student can only observe his technique from a single direction opposite the normal line of sight for that technique. During a normal golf swing, for example, the student will be looking in a forward direction down toward the golf ball and will not be able to assess his technique as it appears in a mirror that is placed off to one side or above his head. Nor do these systems permit assessment of technique from multiple views at once.
Accordingly, what is needed, then, is an inexpensive interactive training system that enables a student to compare his dynamic technique in a sport with that of a master's from whatever view and with whatever pace is most effective in that sport for that particular student.